The modern athletic shoe is a combination of many elements which have specific functions, all of which must work together for the support and protection of the foot during an athletic event. The design of an athletic shoe has become a highly refined science. No longer do athletes and participants in sports events use a pair of "sneakers" for all sports. Athletic shoes today are as varied in design and purpose as are the rules for the sports in which the shoes are worn. Tennis shoes, racquetball shoes, basketball shoes, running shoes, baseball shoes, football shoes, weightlifting shoes, etc., are all designed to be used in very specific, and very different, ways. They are also designed to provide a unique and specific combination of traction, support, and protection to enhance athletic performance. Not only are shoes designed for specific sports, they are also designed to meet the specific characteristics of the user. For example, athletic shoes are designed differently for heavier persons than for lighter persons; differently for wide feet than for narrow feet; differently for high arches than for low arches, etc. Some shoes are designed to correct physical problems, such as over-pronation, while others include devices, such as ankle supports, to prevent physical problems from developing.
An athletic shoe is divided into two general parts, an upper and a sole. The upper is designed to snugly and comfortably enclose the foot. In a running or jogging shoe, the upper typically will have several layers, including a weather and wear resistent outer layer of leather or synthetic material, such as nylon, and a soft padded inner liner for foot comfort. Current uppers typically have an intermediate layer of a synthetic foam material. The three layers of the upper may be fastened together by stitching, gluing or a combination of these. In areas of maximum wear or stress, reinforcements of leather and/or plastic are attached to the upper. Two examples of such reinforcements are leather toe sections attached over synthetic inner layers of the toe area, and heel counters made of an inner layer of plastic in an outer layer of leather.
The other major portion of the athletic shoe is the sole. The sole must provide traction, protection, and a durable wear surface. The considerable forces generated by running require that the sole of a running shoe provide enhanced protection and shock absorption for the foot and leg. Accordingly, the sole of a running shoe typically includes several layers, including a resilient, energy absorbent material as a midsole and a ground contacting outer sole or outsole, which provides both durability and traction. This is particularly true for training or jogging shoes designed to be used over long distances and over a long period of time. The sole also provides a broad, stable base to support the foot during ground contact.
The closure system of an athletic shoe is important to its comfort and fit. In principle, all closure systems serve to secure the shoe upper against the foot. Traditionally, closure systems for athletic and other shoes have included shoelaces which are threaded through eyelets around a throat or tongue opening in the upper portion of the shoe. The placement of the eyelet rows, particularly their distance from a point where the sole and upper meet, influences the effect the laces will have in cinching the upper against the foot. The closure system must be able to adapt to feet of various widths and to varying personal preferences about snugness of fit.
It has also been found advantageous to employ "speedlaces" in athletic shoes. "Speedlaces" employ wide shoelace openings which are larger than the uncompressed cross-section of the shoelace to permit a single pull on the end of the shoelace to easily pull the shoelace through all the openings and tighten the shoelace throughout its lacing pattern with uniform tension. One type of currently available "speedlaces" is formed of a plastic bar from which a plurality of aligned large eyelets extend.
Some users may find a more comfortable shoe fit with different lacing tension over different parts of the foot. For example, the top of the foot, that is the portion over the instep, is sensitive because nerves are nearer to the surface. If the shoe is too tight in this area, the nerve can be aggrevated. However, in other areas, particularly in the toe area and around the ankle area, it may be more comfortable to have tighter tension on the shoelaces. Prior art "speedlace" designs do not allow for adjustable tension; that is, "speedlaces" do not allow the shoelace to apply different tension at different areas along the foot. They permit only a single uniform tension over the entire length of the lacing system.
An adjustable width lacing system offers greater control over the fit of the shoe through the use of staggered eyelets which vary the width across the throat at which the shoelaces apply pressure. Such a lacing system is disclosed in U.S. Pat. No. 4,255,876 to Jeffrey O. Johnson issued on Mar. 17, 1981. Numerous variations can be utilized to create a custom fit: eyelet rows that are placed far apart are often used by runners with narrow feet for a snug fit. Eyelet rows that are placed closely together are recommended for runners with wide feet. Athletes with feet of average width often prefer to lace through all the eyelet pairs. Currently available variable width lacing systems are simply formed as staggered eyelets or openings in the reinforcement strip about the throat of the shoe. Such openings engage the shoelaces with a slight amount of friction, thus preventing the shoelace from being uniformly applying pressure to the foot by pulling on the end of the shoelace.
Lacing closure systems have been disclosed which use lace locking devices, such as restricted diameter eyelets in U.S. Pat. No. 1,434,723 issued to Triay on Nov. 7, 1922. The locking device maintains the preset tension on laces at a paticularly location along the lacing system.